The last decade has witnessed the expanding use of handheld electronic devices. Although handheld devices are easily carried, they rely on power from batteries and further from power supplying devices in case the battery power is exhausted. Handheld electronic devices can be charged through a transformer or voltage converter in compliance with specific requirements. However, the charging voltage designed for one electronic device may be fixed and cannot be adapted to another electronic device.
As personal handheld electronic devices continue to thrive, charging requirements and specifications for different electronic devices become diversified. To address the need to charge different electronic devices, one should prepare more than one transformers or voltage converters to deal with different charging standards. Thus, it may be desirable to improve existing transformers or voltage converters in order to meet the charging requirements for various handheld electronic devices.